Coordinated net-load management

ABSTRACT

A management device includes at least one processor communicatively coupled to at least one energy resource controller controlling at least one energy resource and to at least one deferrable load controller controlling power to at least one deferrable load. The is configured to receive an indication, determined based on a frequency value of an electrical network and a nominal frequency value, that a frequency anomaly event has occurred. Responsive to receiving the indication that the frequency anomaly event has occurred, the processor is also configured to determine, for at least one of the energy resource and the deferrable load, based on the frequency value, the nominal frequency value, and a power value of the electrical network, a respective power command, and cause at least one of the at least one energy resource and the at least one deferrable load to modify operation based on the respective power command.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/298,912, filed Mar. 11, 2019, which claims the benefit of U.S.Provisional Application No. 62/640,876, filed Mar. 9, 2018. The entirecontent of each listed application is incorporated herein by reference.

CONTRACTUAL ORIGIN

The United States Government has rights in this invention under ContractNo. DE-AC36-08GO28308 between the United States Department of Energy andAlliance for Sustainable Energy, LLC, the Manager and Operator of theNational Renewable Energy Laboratory.

This invention was made with Government support under contract numberDE-AR0000701 awarded by DOE, Office of ARPA-E. The Government hascertain rights in this invention.

BACKGROUND

Power systems typically include multiple, distinct frequency controllevels. Primary frequency control is typically implemented locally ateach generator and works autonomously, usually within one to threeseconds after a disturbance. Droop controllers, which adjust speed oroutput of the generator, are one example of primary frequency control.Secondary frequency control includes Automatic Generation Control (AGC),in which a central controller adjusts the active power output ofmultiple generators in an area to restore the frequency and powerinterchanges with other control areas to their target values. Secondaryfrequency control typically occurs within four seconds to five minutesafter a disturbance. Tertiary frequency control response typically takesminutes to hours and is used to address non-urgent events andlonger-lasting effects or for other reasons.

The integration of renewable generation and distributed energy resources(DERs) into the electric system continues at a fast pace and is posed tobe a permanent trend. These resources are typically coupled to the gridusing power electronics rather than rotating generators. The reality ofmore inverter-coupled generation, in addition to related trends, isresulting in decreased system inertia and posing challenges towardstabilizing grid voltage and frequency.

SUMMARY

In one example, a device includes at least one processor communicativelycoupled to at least one energy resource controller that controls atleast one energy resource and to at least one deferrable load controllerthat controls power to at least one deferrable load. The at least oneprocessor is configured to receive an indication, determined based on afrequency value of an electrical network and a nominal frequency value,that a frequency anomaly event has occurred. The at least one processoris also configured to, responsive to receiving the indication that thefrequency anomaly event has occurred, determine, for at least one of theat least one energy resource and the at least one deferrable load, basedon the frequency value, the nominal frequency value, and a power valueof the electrical network, a respective power command, and cause atleast one of the at least one energy resource and the at least onedeferrable load to modify operation based on the respective powercommands.

In another example, A system includes a grid point of common coupling(PCC) controller configured to measure a frequency value of anelectrical distribution network at a point at which the electricaldistribution network connects to a consumer electrical system,determine, based on the frequency value and a nominal frequency value,whether a frequency anomaly event has occurred, and responsive todetermining that the frequency anomaly event has occurred, output anindication of the frequency anomaly event. The system also includes anet-load management device comprising at least one processor, whereinthe net-load management device is configured to receive the indicationof the frequency anomaly event, output a request for a respectivepresent operating power value for at least one deferrable load in theconsumer electrical system, and receive an indication of the respectivepresent operating value for the at least one deferrable load. Thenet-load management device is further configured to, responsive toreceiving the indication of the frequency anomaly event, determine, forthe at least one deferrable load, based on the respective presentoperating value, the frequency value, and a nominal frequency value, arespective power command, and output an indication of the respectivepower command. The system further includes at least one deferrable loadcontroller operatively coupled to the at least one deferrable load. Theat least one deferrable load controller is configured to receive theindication of the respective power command and cause the at least onedeferrable load to modify operation based on the respective powercommand.

In another example, a method includes receiving, by a computing devicecomprising at least one processor, an indication, determined based on afrequency value of an electrical network and a nominal frequency value,that a frequency anomaly event has occurred. The computing device iscommunicatively coupled to at least one energy resource controller thatcontrols at least one energy resource and to at least one deferrableload controller that controls power to at least one deferrable load. Themethod further includes, responsive to receiving the indication that thefrequency anomaly event has occurred: determining, by the computingdevice and for at least one of the at least one energy resource and theat least one deferrable load, based on the frequency value, the nominalfrequency value, and a power value of the electrical network, arespective power command, and causing, by the computing device, at leastone of the at least one energy resource and the at least one deferrableload to modify operation based on the respective power command.

The details of one or more examples are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual diagram illustrating an example consumerelectrical system using coordinated net-load management, in accordancewith one or more aspects of the present disclosure.

FIG. 2 is a set of graphical plots illustrating experimental performanceof coordinated net-load management, in accordance with one or moreaspects of the present disclosure.

FIG. 3 is a conceptual diagram illustrating an example grid system usingcoordinated net-load management, in accordance with one or more aspectsof the present disclosure.

FIG. 4 is a flow diagram illustrating example operations for performingcoordinated net-load management, in accordance with one or more aspectsof the present disclosure.

DETAILED DESCRIPTION

The techniques of the present disclosure provide primary frequencyresponse using flexible load and DERs. Specifically, the systems,devices, and/or methods described herein may be used to coordinate agroup of flexible loads and controllable DERs in real time or near-realtime to provide fast (e.g., within about 10 AC cycles or within about200 ms) frequency reserves that can serve as a step response for primaryfrequency control. As one example, a management device (also referred toherein as a load controller unit) may be installed in a residential orcommercial building and be operatively connected to one or more DERs andone or more loads. The management device may be configured to monitorthe grid for frequency events. If an event is detected, the managementdevice may consider various objectives while causing the DERs and/orloads to modify operation in order to provide primary response to thegrid. That is, the management device may determine statuses of devicesunder its control, develop a strategy for providing the primary responsebased on one or more objectives, and cause the devices under control toimplement the strategy all within about 10 AC cycles.

With the increase in inverter-coupled generation and related trends,techniques for stabilization of grid voltage and frequency will need toincorporate increased participation from DERs. With continuingdeployment of information and communication infrastructure, flexible andcontrollable load can become effective resources for grid frequencyregulation when aggregated and coordinated together to create virtualpower plants as described herein. In contrast to related-art approaches,the techniques of the present disclosure involve individual loadscommunicating with a centralized master controller that determines anoptimal approach for dispatching controllable DERs and deferrable load.

The techniques of the present disclosure leverage high-speed localmeasurements and ensure that local objectives, which could potentiallyvary over time, are met. By obtaining accurate or “recent” informationto perform frequency response, the techniques described herein maygreatly reduces the uncertainty of the outcome and avoids the need forforecasting. That is, by quickly determining and implementing asolution, it is less likely that the situation has already changed.These techniques also offer coordination and optimal control advantageson a fast timescale that is suited for primary frequency control. Thetechniques herein may be used at a building or plant scale, whereflexibility across multiple building net-load devices can be leveraged,but are also well suited for inclusion in hierarchical or aggregatedschemes. For instance, master controllers may control multiple (e.g., 5,10, or other number) homes or buildings, and distributed or centralizedcontrol of such groupings may hierarchically leverage hundreds or eventhousands of homes or buildings.

FIG. 1 is a conceptual diagram illustrating an example consumerelectrical system (e.g., system 102) using coordinated net-loadmanagement, in accordance with one or more aspects of the presentdisclosure. In the example of FIG. 1, system 102 includes managementdevice 103, energy resources 104A and 104B (collectively “energyresources 104”), inverter 106, deferrable loads 108A-108D (collectively“deferrable loads 108”), non-deferrable loads 110, and local network112. Inverter 106, deferrable loads 108, and non-deferrable loads 110may all be connected on a common electrical bus. System 102 alsoincludes PCC SCCN 114, inverter SCCN 116, load SCCNs 118A-118D(collectively “load SCCNs 118”), and utility meter 120. System 102represents only one example of an electrical system using coordinatednet-load management, and the techniques described herein may be used invarious other systems having more, fewer, or different components thanthose shown in the example of FIG. 1.

Management device 103, in the example of FIG. 1, represents a computingdevice configured to implement the coordinated net-load managementtechniques detailed herein. In some examples, management device 103 maybe a computer, such as a desktop computer, a laptop computer, a servercomputer, or other computer. In some examples, management device 103 maybe a computing device that is custom designed to perform the techniquesof the present disclosure.

In the example of FIG. 1, management device 103 includes one or moreprocessors 105. Processors 105 may implement functionality and/orexecute instructions within management device 103. For example,processors 105 may receive and execute instructions, thereby enablingthe functionality of management device 103. In some examples, processors105 may represent an application specific integrated circuit (ASIC) orfield programmable gate array (FPGA) that was designed and/or configuredto perform the net-load management techniques described herein.

In the example of FIG. 1, energy resources 104 each represent a deviceor system capable of generating electrical power that can be fed (e.g.,via an inverter or other device, in some examples) into an electricalnetwork. In the example of FIG. 1, for instance, energy resource 104A isshown as a PV array and energy resource 104B is shown as a battery orenergy storage system. Other examples of energy resources include windturbines, generators (e.g., gas generators, etc.), fuel cells, electricvehicles, and others. Though not shown in the example of FIG. 1 forbrevity, energy resources 104 may include independent, intermediatepower electronic converters (e.g., a DC-DC converter to enable maximumenergy extraction from the solar array via maximum power point tracking)between their outputs and the input to inverter 106.

Inverter 106, in the example of FIG. 1, represents power electronicsconfigured to manage the power output of one or more energy resources.For instance, inverter 106 may receive power from energy resources 8Aand 8B and transform the power into a form that can be transmitted viathe connected electrical system. Power inverters, in general, mayperform various operations to modulate the amount of power beingtransferred and make the power output of energy resources more stableand/or more compatible with power networks. In some examples, inverterssuch as inverter 106 may output both active and reactive power. Forsimplicity, the techniques described herein are explained with a focuson active power. Reactive power, however, may be important for othersystem functions like regulating the voltage throughout a distributionnetwork to stay within safe levels.

In the example of FIG. 1, deferrable loads 108 and non-deferrable loads110 represent any number of common power consumption devices. Commonresidential examples of deferrable loads 108 and/or non-deferrable loads110 may be a refrigerator, an oven, lights, a plug-in space heater, amicrowave, a water heater, a dishwasher a washing machine, a dryer, anair conditioner, an electric vehicle charging station, or any otherdevice that consumes power.

Whether a load is a deferrable load or a non-deferrable load may bedetermined in a number of ways. In some examples, a user or manager ofthe devices may decide whether a load is deferrable or not. Forinstance, perhaps a user determines that the fridge, oven, water heater,and space heater are deferrable, because these devices intrinsicallycontain thermal energy storage and so can be curtailed to some degreewithout much effect on the user. On the other hand, the user maydesignate the lights, dishwasher, washing machine, dryer, and airconditioner as non-deferrable loads, because these may be devices theoperation of which the user is not willing to compromise on. In someexamples, the technical capabilities (e.g., required power quality,necessary communication technology, etc.) of a device may determinewhether the device is deferrable or not. For instance, a computerrequiring constant, uniform input power and sensitive to interruption atshort notice, may not be able to be a deferrable load. In some examples,other means of determining whether loads are deferrable or not may beadditionally or alternatively employed.

Deferrable loads, generally, may include controllable loads andnon-controllable loads. Controllable loads may be those loads that canbe given a continuous value as a load set point command.Non-controllable loads may be those loads with no capability ofreceiving or acting upon a load set point. Examples of a controllabledeferrable load may be an electric vehicle charging station, dimmablelights, a plug-in heater with multiple or fully-variable controlsettings, or a variable-speed pool pump. Examples of non-controllabledeferrable loads may include most legacy devices that cannot bemodulated, but only turned “on” or “off” For simplicity, in the exampleof FIG. 1, all of deferrable loads 108 are non-controllable loads.

Local network 112, in the example of FIG. 1, represents anycommunication infrastructure sufficient to allow the communicationdescribed herein. For example, local network 112 may be a wired orwireless internet protocol (IP) network allowing for ease of integrationand scalability. In such example, local network 112 may include networkcables, network switches, IP routers, wireless access points, wirelessadapters, or any other equipment usable to implement an IP network. Asanother example, local network 112 may be another type of wired orwireless network, such as serial communications bus or cellular wirelessnetwork. Note that local network 112 should not introduce significantlatency into the communications between devices, given the primaryresponse nature of the techniques described herein.

In the example of FIG. 1, the point of common coupling (PCC) to thedistribution network is interfaced to a control layer (represented bythe dashed lines in FIG. 1) via PCC SCCN 114. PCC SCCN 114 represents aflexible Sensing, Communication, and Control Node (SCCN). PCC SCCN 114may be configured to measure various electrical parameter values (e.g.,frequency, voltage, current, or other values) of the power beingprovided to system 102 from utility meter 120. PCC SCCN 114 may also beconfigured to transmit such parameter values (e.g., via local network112) to management device 103 and, in rare circumstances and uponcommand, disconnect the entirety of system 102 from the local gridconnection.

In the example of FIG. 1, inverter 106 is interfaced to the controllayer through inverter SCCN 116. Inverter SCCN 116 represents a flexibleinterface configured to measure various electrical parameter values ofthe power being provided (or absorbed) by inverter 106 and transmit suchparameter values (e.g., via local network 112) to management device 103.Inverter SCCN 116 may also be configured to receive (e.g., via localnetwork 112) dispatch commands from management device 103 and causeinverter 106 to modify operation accordingly. For example, inverter SCCN116 may receive an active power set point determined by managementdevice 103 and provide the set point to a local controller of inverter106. Inverter 106 may then modify operation to output the active powerspecified by the set point

In the example of FIG. 1, each of deferrable loads 108 is interfaced tothe control layer through one of load SCCNs 118. For example, load SCCN118A corresponds to deferrable load 108A, and so on. Load SCCNs 118represent flexible interfaces configured to measure various electricalparameter values of the power being absorbed by deferrable loads 108 andtransmit such parameter values (e.g., via local network 112) tomanagement device 103. Load SCCNs 118 may also be configured to receive(e.g., via local network 112) dispatch commands from management device103 and cause the corresponding one of deferrable loads 108 to modifyoperation accordingly. In some examples, such as when deferrable loads108 are controllable loads, a load SCCN may cause the load to modifyoperation by transmitting a power set point to the load. In someexamples, such as when deferrable loads 108 are non-controllable loads,a load SCCN itself may control power delivery to the load. That is, fornon-controllable loads, a load SCCN may include means (e.g., a switchingmechanism) for connecting and disconnecting the non-controllable load,making it dispatchable. As all of deferrable loads 108 arenon-controllable loads in the example of FIG. 1, all of load SCCN s 118may include switches or other mechanisms to cut off power to therespective deferrable loads 108 based on received dispatch commands.

In general, SCCNs may provide the necessary functionality to facilitatethe techniques described herein. Depending on the associated device, theSCCN may make or obtain measurements, provide the measurements to themanagement device, receive dispatch commands from the management device,and act on or pass on the dispatch commands. For instance, in someexamples, SCCNs may continuously collect and process (e.g., usingfilters, frequency calculation, etc.) analog inputs as neededrepresenting voltage and current measurements of the associated device.In some examples, SCCNs may buffer (e.g., store) these measurements sothat a recent measurement is always available to be sent back to amanagement device immediately upon request (i.e., without any delay fora new measurement to be taken). In some examples, SCCNs may, based onthese measurements, determine the control capacity that is possible forthe associated device, and report this capacity to the managementdevice. The determined control capacity could be used for instance, toimplement minimum or maximum run times for a particular appliance toavoid damaging that appliance.

In some examples, SCCNs may organize/package the measurements andcommands into a format expected by the management device. SCCNs may, insome examples, handle communications with the management device over aspecified protocol. In some examples, SCCNs may receive dispatchcommands from the management device, verify the dispatch command iswithin capability of the associated device, and act on the commandand/or pass the command to the associated device.

The functionality of an SCCN depends on the associated device. Forinstance, an inverter normally has a controller to manage its poweroutput. Thus an inverter SCCN may not need to control the power outputof the inverter itself, but rather pass commands to the inverter in acompatible format. Some deferrable loads (e.g., certain “smart” devices)also have such capability. However, these capabilities often lacksufficient speed and/or the ability to provide certain measurements,thus an SCCN may instead act on dispatch commands itself to modifyoperation of the deferrable load. In such instances, the load may or maynot be capable of reduction. Some devices, for instance, may only beable to be turned “on” or “off.” In such instance, an SCCN may use asimple switching mechanism to cutoff power to the load. On the otherhand, some devices may have multiple power settings or variable powersettings. In such instance, an SCCN may use other techniques to adjustthe power to the load, such as pulse width modulation (PWM) or othersuitable techniques. In the future, SCCNs may be incorporated into oneor more devices. For instance, loads (e.g., smart appliances), PCCdevices (e.g., smart meters), and/or energy resource devices (e.g.,power inverters) may include some combination of hardware, software,and/or firmware that enables the device to perform some or all of thefunctionality of SCCNs as described herein.

While shown and described herein as each corresponding to a singledevice, SCCNs may, in other examples, correspond to more than onedevice. For example, load SCCNs 118 may actually be a single load SCCNto which all four of loads 108 is connected. As another example,inverter SCCN 116 and PCC SCCN 112 may be combined in some examples andthe unified SCCN may perform functions of both SCCNs 112 and 116.

In the example of FIG. 1, utility meter 120 represents a metering deviceconnecting a residential, commercial, or other consumer to a powerdistribution grid (not shown). Utility meter 103 may be a conventionalmeter, a smart meter, or any other utility meter.

A collection of loads (both deferrable and non-deferrable) andinverter-interfaced energy resources behind a typical electric customermeter is referred to herein as a “net-load” unit. In the example of FIG.1, for instance, energy resources 104, inverter 106, deferrable loads108, and non-deferrable loads 110 may represent a net-load unit.

The power imported from the grid (e.g., through utility meter 120) isgiven by P_(G,grid)(t) and the capacity limits can be defined asP_(G,grid) ^(min)≤P_(G,grid)(t)≤P_(G,grid) ^(max). The power supplied byinverter 106 is defined as P_(G,inv)(t), where P_(G,inv)(t)>0 wheninverter 106 is supplying power to the AC bus and P_(G,inv)(t)<0 wheninverter 106 is absorbing power from the AC bus. Inverter 106 should beoperated within its ratings P_(G,inv) ^(min)≤P_(G,inv)(t)≤P_(G,inv)^(max) and could be unidirectional (P_(G,inv) ^(min)=0) or bidirectional(P_(G,inv) ^(min)<0). Inverter 106 may switch to a different power setpoint in response to receiving a dispatch command P*_(G,inv). Inverterresponse to a dispatch command P*_(G,inv) can be very fast. An inverterreference tracking response time of less than two cycles isexperimentally shown herein with a custom inverter, though this responsetime can be slower for other inverters.

Let P_(L)(t)={P_(L,i)(t)}_(i=1) ^(N) ^(L) represent the set of powerdemands from the N_(L) non-deferrable loads (e.g., non-deferrable loads110) and P_(Ld)(t)={P_(Ld,i)(t)}_(i=1) ^(N) ^(Ld) represent the set oftime-varying power demands from the N_(Ld) deferrable loads (e.g.,deferrable loads 108). Deferrable loads 108 may be turned on or offresponsive to receiving a command q*_(LD,i)(t)∈{0,1} such that theeffective power is {circumflex over(P)}_(Ld,i)(t)=q*_(Ld,i)(t)P_(Ld,i)(t). By Kirchoff's laws, the (ideal)power consumed from the grid is therefore: P_(G,grid)=Σ_(i) ^(N) ^(L)P_(L,i)+Σ_(i) ^(N) ^(Ld) P_(Ld,i)−P_(G,inv). The power consumed orsupplied at each point, and deferrable load commands are all assumed tobe time-varying quantities. The time dependence (t) is dropped for easeof notation in some cases herein.

Assume that the net-load unit shown in FIG. 1 is incentivized by thelocal system operator, a local aggregator, or other entity to provide anet-load response upon detection of a frequency anomaly event in thedistribution network. Example incentives may include monetary or otherbenefits to the consumer. A frequency anomaly event may be defined to bewhen f(t)<(f_(nom)−δ_(f,low)) or f(t)>(f_(nom)+δ_(f,high)), wheref_(nom) is the nominal grid frequency and δ_(f,low) and δ_(f,high) arenominal frequency limits (in Hz) below and above f_(nom). When frequencyoutside these limits is detected, the net-load unit may respond suchthat:P* _(G,grid)(t _(e)+τ)=(1−η sign(f(t _(e))−f _(nom)))P _(G,grid)(t_(e))  (1)where t_(e) represents the instant in time in which a frequency anomalyevent is detected, τ is the unit's response time, η∈[0.0,1.0] is aparameter defining what percentage of a net-load unit's power outputmust be curtailed or increased (i.e., a participation factor), f(t_(e))is the measured grid AC frequency at t=t_(e), P_(G,grid) is the measuredpower transfer at the grid PCC, and P*_(G,grid) is the grid powercommand. In practice, P*_(G,grid) is determined by the η agreed upon bythe net-load unit operator and the aggregator or system operator.

While a net-load unit operator (e.g., a homeowner) may provide thisnet-load response in exchange for the received incentive, the operatormay desire to do so in a particular fashion or while preventing certainoccurrences. These desires represent control objectives. The techniquesof the present disclosure are designed to be flexible such that they canincorporate a variety of control objectives. In the example of FIG. 1,for instance, the net-load unit operator may desire to provide theprimary response with minimal inconvenience to him- or herself byavoiding the total amount of load that must be curtailed (a likelyobjective for real-world consumers). Consequently, management device 103may be configured to implement the example control objective ofminimizing the total amount of load that must be deferred whileproviding the frequency response.

The objective in the example of FIG. 1 thus becomes to provide thedesired net-load response by prioritizing the dispatch of inverter 106and, if the inverter's response cannot satisfy the overall net-loadresponse requirement, curtail the minimum possible amount of deferrableloads 108 to meet the requirement. This objective can be formalized as:

$\begin{matrix}{\max\limits_{q^{*}}{\sum_{i = 1}^{N_{Ld}}{c_{i}{{\overset{\hat{}}{P}}_{{Ld},i}\left( {t_{e} + \tau} \right)}}}} & (2) \\{{{subject}\mspace{14mu}{to}\mspace{14mu}{P_{G,{grid}}\left( {t_{e} + \tau} \right)}} = {P_{G,{grid}}^{*}\left( {t_{e} + \tau} \right)}} & (3) \\{P_{G,{inv}}^{\min} \leq {P_{G,{inv}}(t)} \leq P_{G,{inv}}^{\max}} & (4) \\{P_{G,{grid}}^{\min} \leq {P_{G,{grid}}(t)} \leq {P_{G,{grid}}^{\max}.}} & (5)\end{matrix}$where c_(i)=1∀i. It is important to note, however, that the developedframework is flexible, such that a variety of other user objectives canbe achieved in accordance with the techniques described herein. Forexample, using c_(i)=1∀i in equation (2) makes the cost associated witheach individual (i=1 . . . N_(Ld)) load decision equal to the capacityof the load, thus resulting in an optimal solution that minimizes thetotal amount of load that must be curtailed. However, if the userinstead wished to prioritize some loads over others in a particularorder, the c_(i) for each load could be individually set with lowpriority loads given a higher cost by the user to achieve this end. Thec_(i) term is user modifiable and can be time-varying such that a usercould set each c_(i) to be very large during periods when they wish tohave load curtailment only in rare cases (and for which they will bemore highly compensated) or set relatively lower in times when the usermay be more tolerant of load curtailment actions.

The parameter η in equation (1) is a value agreed upon by the net-loadunit operator (e.g., a homeowner or building manager) and the poweraggregator or power system operator. In practice, this process occursbest when, first, the net-load unit operator determines a set offeasible η that it can achieve along with the associated cost of each η.Second, this information is communicated to the system operator who thenmakes system-level optimal decisions based upon the sets of feasible ηand associated costs received from each net-load unit participatingwithin the system operator's net-load coordination group. Finally, thesystem operator sends chosen η values to each net-load unit for action.This procedure helps ensure that the local net-load unit can implementits own set of objectives and preferences and that a given η isfeasible. As an example of an infeasible η, high values of η (i.e.,approaching 1.0) would occur if the local net-load unit contained a highcapacity of non-deferrable load vs. deferrable loads.

In accordance with the techniques described herein, management device103 is configured to leverage high-speed measurements from each net-loadresource (e.g., obtained via SCCN s 114, 116, and 118) and analgorithmic implementation of control objectives to provide the optimaland coordinated dispatch of resources within a net-load unit for use asprimary frequency response. As time is of the essence, management device103 should be able to communicate to all net-load resources and solvethe algorithm associated with the control objective(s) in a rapid (e.g.,less than about 10 ac cycles or less than about 200 ms) manner. Thetechniques of the present disclosure provide a centralized mastercontroller (e.g., management device 103) for coordinated, optimaldispatch of all net-load resources; realize and employ a high-speedcommunication network (e.g., local network 112) between net-load unitdevices and the master controller; provide flexible communicationinterfaces (SCCN s 114, 116, and 118) to the control layer at eachnet-load resource; and implement physical interfaces for high-speedmeasurement and connection/disconnection of electrical loads (e.g.,deferrable loads 108).

These techniques were experimentally demonstrated and verified using aresidential-scale testbed and one example control objective ofminimizing the total load deferred while meeting the frequency responsetarget. However, as previously stated, the techniques are flexible inthat it is possible to utilize other load/resource combinations andcontrol objectives. The demonstration was performed using a net-loadunit consisting of an inverter and four household appliances in theEnergy Systems Integration Facility at the National Renewable EnergyLaboratory in Golden, Color. As the primary aim of the experiment was todemonstrate the performance of the framework and the particular loadmanagement algorithm implemented, the four appliances were allconsidered as deferrable loads and no non-deferrable loads wereincluded. The specific devices used were a 120V combinationrefrigerator/freezer (General Electric Profile PSQS6YGY); bank offifteen 120V compact fluorescent and incandescent light bulbs; a 120Vplug-in electric heater; a 240V combination Range/Oven (Maytag MER8674);and a 120V, 1 kW (P_(G,inv) ^(max)=1000 W) inverter (custom).

Raspberry Pi 3 ARM-based controllers were used to implement SCCNs 116,and 118 in the demonstration. Given the fact thatP_(G,grid)=Σ_(i)P_(Ld,i)−P_(G,inv) for this example demonstration, noGrid PCC Measurement Controller (i.e., SCCN 114) was needed; the totalnet-load P_(G,grid)(t) was determined using deferrable load and invertermeasurements directly. Grid frequency anomaly detection was implementedusing a quadrature phase locked-loop (QPLL) implemented on the custominverter's local controller (as opposed to performed by a PCC SCCN asdescribed elsewhere herein). Reliably measuring frequency during rapidtransients and making a control decision within the desired time limitcan be challenging. However, this QPLL implementation—with a choice ofgains that traded-off overshoot and settling time—provided reliable,settled, measurements within 1-3 AC cycles throughout all rapidtransients tested.

The open source ZeroMQ distributed messaging platform was used toimplement the control layer, with information being passed betweendevices using the Transmission Control Protocol (TCP). The implementedSCCNs published measurements and statuses from each net-load resourceonto the ZeroMQ message bus and subscribed to requests and commands fromManagement device 103 on the same message bus. The controller ofinverter 106 and inverter SCCN 116 were interfaced using serialcommunication.

While related-art solutions for controlling loads exist, none were foundthat natively support on/off control of loads and report high-speedmeasurements at adequate speed (e.g., less than about 10 ac cycles orless than about 200 ms). Instead, related art solutions are designed forslower speeds and in many cases do not include sensors. Thus, load SCCNswere implemented by custom making physical interfaces for high-speedmeasurement and connection/disconnection of electrical loads. Thesedeferrable load control interfaces are simple to use by connecting inseries with the appliance or load's normal house wiring connection usingstandard NEMA connectors. Each interface includes a solid state relay;fuses for overcurrent protection; high-bandwidth (˜200 kHz) voltage andcurrent sensors; analog RMS-to-dc converters; and a control layercommunications interface for processing of measurements and interfacingwith the control layer.

Management device 103 needed to be able to communicate to all net-loadresources and solve the algorithm associated with the control objectiveefficiently. In the demonstration, a Raspberry Pi 3 was used toimplement the management device, as this met these requirements.However, more powerful local controllers can be leveraged for larger ormore complex systems and less powerful controllers could likely be usedto achieve lower cost.

The optimization problem described by (2)-(5) was implemented in themanagement device using Algorithm 1. This algorithm determines theoptimal inverter set point P*_(G,inv) and the optimal set of deferrableloads on/off set points {q*_(Ld)}_(i=1) ^(N) ^(Ld) that minimize thetotal amount of load that must be deferred, while achieving the desiredgrid import power P*_(G,grid)(t_(e)+τ) as closely as possible. Algorithm1 was designed for use with residential buildings in which deferrableloads are often appliances that can be shut off quickly (using SCCNs),but may not be able to be turned on and a known operating point achievedquickly. Thus, in the demonstration, both deferrable load and invertergeneration were used for response to underfrequency events, but onlyinverter generation was used for response to overfrequency events. Inother examples, deferrable loads may be used to respond to bothunderfrequency and overfrequency events.

Algorithm 1 - Example Net-Load Management Control Implementation INPUT:P_(Ld)[1..N_(Ld)], P_(G,inv), P_(G,inv) ^(min), P_(G,inv) ^(max),P_(G,grid), η, f(t_(e)), f_(nom) DO: Calculate P_(G,gridΔ) = ηsign(f_(nom) − f(t_(e))) P_(G,grid) //Dynamically build the array of allfeasible load actions: Let P_(Ldo)[1..N_(Ld)] be an array of objectswith entries P_(Ldo)[i].power = P_(Ld)[i] and P_(Ldo)[i].idx = i for alli = 1..N_(Ld) Let P_(Ldp)[1..N_(Ldp)] be an array of all objects inP_(Ldo) where P_(Ldo)[i].power > 0 sort P_(Ldp) in ascending order byP_(Ldp)[i].power Let P_(La) be an empty array //all possible total loadset points P_(La)[1] = 0 //corresponds to the case where no loads arecurtailed P_(La)[2] = P_(Ldp)[1].power //case of only the smallest loadis curtailed for i = 1..(N_(Ldp) − 1) for j = 1..2^(i) P_(La)[2^(i) + j]= P_(La)[j] + P_(Ldp)[i + 1].power if (P_(La)[2^(i) + j] > P_(G,gridΔ)//all feasible load actions needed for this P_(G,gridΔ) have been addedbreak out of both for loops Let N_(La) = |P_(La)| be the length ofP_(La) //first, allocate all available inverter capacity if (P_(G,inv)^(max) − P_(G,inv)) ≥ P_(G,gridΔ) P*_(G,inv) = P_(G,inv) + P_(G,gridΔ)P_(G,gridΔ) = 0 else P*_(G,inv) = P_(G,inv) ^(max) P_(G,gridΔ) =P_(G,gridΔ) − P*_(G,inv) //if further reduction required, curtail theminimum total amount of load that achieves the required grid powerreduction if P_(G,gridΔ) > 0 for i = 1..N_(La) if (P_(La)[i] ≥P_(G,gridΔ)) or i = N_(La) //build the set of all q*_(Ld,i) based on theresulting optimal P_(La)[i] Let ix[1..N_(b)] be an array with entriescorresponding to the N_(b)-bit binary representation of (i − 1) with theLSB in ix[1] //e.g., 4 = [0,0,1] for j = 1..N_(b) idx_(orig) =P_(Ldp)[j].idx //get the index corresponding to load P_(Ldp)[j] in theoriginal array q*_(Ld)[idx_(orig)] = (1 − ix[j]) //curtail cmd. Formatto on/off format P_(G,gridΔ) = P_(G, gridΔ) − P_(La)[i] Break //reduceinverter output by any load curtailment overshoot to //achieve theminimum deviation from desired grid power if P_(G,gridΔ) < 0 P*_(G,inv)= P*_(G,inv) + P_(G,gridΔ) if P*_(G,inv) < P_(G,inv) ^(min) P*_(G,inv) =P_(G,inv) ^(min) OUTPUT: P*_(G,inv), {q*_(Ld,i)}_(i=1) ^(N) ^(Ld)

While omitted for brevity, it can be proved that Algorithm 1 achievesthe optimal solution to (2)-(5) when: 1) the net-load unit includes asufficient amount of deferrable load and inverter-based energyresources; 2) a reasonable η is used for the net-load resourcesavailable; and 3) an underfrequency event occurs. The implementedalgorithm leverages dynamic programming to efficiently and dynamicallydetermine the cost associated with each possible load deferment actionfrom the bottom up. It can be shown that a simple greedy strategy willnot work here. Greedy approaches follow a set heuristic, called thegreedy choice, for selecting the best choice at each decision point withthe intent that this will lead to finding the global optimum. Forexample, in this problem greedy choices of using all available invertercapacity and then (i) always picking the smallest (and thus lowest cost)load that is below the desired net-load reduction set point, (ii) alwayspicking the absolute smallest load, or (iii) always picking the loadthat is just above the net-load reduction set point seem like reasonablestrategies to follow. However, the three test cases in Table I, below,provide counter-examples for these three amongst other possible greedychoices. In particular, Test Case #1 shows that greedy choices (i) and(ii) do not result in the optimal solution, and Test Cases #2 and #3show that greedy choice (iii) is also not globally optimal.

As previously described, the control objective implemented was tominimize the total amount of load deferred while providing the desirednet-load response. The following test cases examined three scenariosinvolving the same loads and inverter, but varying net-load responsetarget (varying η) and actual load measurements. Each test case beganwith the appliances turned on for some time and the inverter exportingpower at ˜80% (800 W) of its nominal power rating. A step in gridfrequency from 60 Hz to 59.7 Hz was then initiated. The inverterdetected the frequency anomaly (δ_(f,low)=0.25 Hz was used). For eachtest case, the measurements listed in the “Start” column of Table I werereceived from each resource by the master controller (management device103). The master controller then determined final load on/off status andinverter set points as shown in the “Finish” column based on the resultsobtained by executing Algorithm 1.

TABLE I Input Conditions and Final Results for Test Cases Measured Power(W) at Start and Finish of Case Test Case #1 Test Case #2 Test Case #3(η = 0.09) (η = 0.14) (η = 0.17) Resource Start Finish Start FinishStart Finish Fridge (I1) 146 146 175 175 147 0 Lights (I2) 411 0 409 0402 0 Plug-in 1360 1360 1360 1360 1345 1345 Heater (I3) Oven (I4) 28272827 2850 2850 2793 2793 Inverter −797 −742 −801 −911 −802 −949 Total3947 3591 3993 3436 3885 3227 ΔP_(G, grid) 9.02% 13.95% 16.94% Response142.6 141.8 141.9 Time (ms)

In Test Case #1, 9% (355 W) of the total measured net-load needed to bedeferred. This amount was more than the smallest load and the remaininggeneration capacity of the inverter and so the next largest load (411 W)had to be curtailed. However, once curtailed, constraint (3) determinedthat the optimal solution should defer as nearly 9% of the net-load aspossible. Thus, Algorithm 1 resulted in the inverter's output beingreduced.

In Test Case #2, 14% (559 W) of the measured netload was to becurtailed. This required at a minimum that the second largest load (409W) be curtailed. However, after that load was curtailed the smallestload (175 W) could also have been curtailed but it was not, because theinverter's remaining capacity (200 W) was sufficient to meet the desiredset point and the main objective (2) is to minimize the amount of loadto be curtailed when possible.

Test Case #3 required a little larger net-load curtailment (17%, 660 W)than Test Case #2. That made the lights curtailment and inverter outputincrease no longer sufficient to meet the net-load curtailmentrequirement. Thus, the optimal solution was to curtail both of the twosmallest loads and then meet the remaining net-load reductionrequirement using an increased inverter output. In all three test cases,the entire sequence of operations, from detection and measurement of afrequency anomaly to completed actuation of coordinated net-loadresponse, was completed within 143 ms (about 8.5 cycles).

FIG. 2 is a set of graphical plots illustrating experimental performanceof coordinated net-load management, in accordance with one or moreaspects of the present disclosure. Specifically, FIG. 2 shows waveformresults for Test Case #3. The top plot shows instantaneous currentmeasurements for each deferrable load including a fridge (represented bytrace I1 in FIG. 2), a bank of light bulbs (represented by trace I2 inFIG. 2), a plug-in heater represented by trace I3 in FIG. 2), and anoven (represented by trace I4 in FIG. 2). The bottom plot shows the gridvoltage (represented by trace V in FIG. 3), calculated grid frequency(represented by trace FREQ in FIG. 2), and inverter current (representedby trace I_INV in FIG. 2). It can be seen that the entire net-loadresponse sequence is completed within 142 ms (˜8.5 ac cycles).Thermostatically-controlled loads (e.g., the fridge and oven) and otherloads (e.g., the lights and plug-in heater) were purposely included todemonstrate that both types can be leveraged by the disclosedtechniques.

FIG. 3 is a conceptual diagram illustrating an example grid system(e.g., system 402) using coordinated net-load management, in accordancewith one or more aspects of the present disclosure. System 402represents a broader application of the techniques described herein andachieves coordinated system-wide net-load management for provision ofgrid primary frequency response using two or more Net-Load CoordinationUnits or NCLUs. Each NLCU may include one or more inverter-interfacedenergy resources, one or more deferrable loads and a management device.For instance, management device 103, energy resources 104, inverter 106,deferrable loads 108, and non-deferrable loads 110 as described withrespect to FIG. 1 may represent one example of a NCLU. System 402includes NLCUs 404A-404E (collectively “NLCUs 404”) as part of powerdistribution system 408A. System 402 also includes larger power system420. Larger power system 420 includes power distribution systems408B-408F, which may each include their own collection of NLCUs.

In the example of FIG. 3, system 402 also includes supervisory controldevice 406. In some examples, however, a supervisory control device 406may not be included. That is, in some examples system-wide net-loadmanagement may utilize only distributed communication and control whilein other examples, system-wide net-load management may additionally oralternatively use centralized communication and control. System 402represents only one example of a grid system using coordinated net-loadmanagement, and the techniques described herein may be used in variousother systems having more, fewer, or different components than thoseshown in the example of FIG. 3.

The management device of each of NLCUs 404, as well as the NLCUs in eachof power distribution systems 408B-408F, may communicate using wired orwireless means, with its respective set of deferrable loads andcontrollable generation to implement coordinated net-load management asdetailed herein. As previously described, deferrable loads includecontrollable loads (i.e., those that can be given a continuous value asa load set point command) and non-controllable loads (i.e., those withno capability of receiving or acting upon a load set point).Non-controllable loads are connected to the NLCU's power system througha deferrable load control interface, which provides a means forconnecting and disconnecting the non-controllable load, making itdispatchable.

The management devices of the NLCUs 404, as shown in FIG. 3, maycommunicate using one or both of the following methods: i) distributedcommunication among one or more of NLCUs 404 and ii) directcommunication with supervisory control device 406, if existent.

A coordinated system primary frequency response using multiple NLCUs mayconsist of two phases. In a pre-event resource identification phase,NLCUs and, if available, a supervisory controller, may communicateperiodically with one another to update location, capacities, andconstraints of all units and to determine how NLCUs will be groupedtogether into larger coordinated units, each referred to herein as aNet-load Coordination Group (NLCG), which will respond in a coordinatedfashion in the event of a grid frequency anomaly.

NLCG selection may be determined by identifying NLCUs that are closeenough (communication latency-wise) to be able to achieve coordinatedresponse on a particular timescale. For instance, if management devicesof a number of NLCUs can each communicate with all the others withinless than two seconds, less than one second, or some other duration, themanagement devices may define their NLCUs as a NLCG. The particulartimescale for defining a NLCG this way may be locally defined (e.g., bya distribution system manager, by users, or by other entities). NLCGsmay be defined in other ways in other examples.

In a coordinated event response phase, when a frequency event occurs,pre-organized NLCGs may each coordinate an optimal grid frequencyresponse using their constituent NLCUs. The management device of eachNLCU may gather local operating states and communicate this informationto neighboring NLCUs (in the case of no supervisory controller beingavailable) or directly to the supervisory control device (if available).When a supervisory control device is available, it may determine acentralized, optimal, problem solution by gathering state informationfrom all connected NLCUs, solving an optimization problem, and thensending control set points to each NLCU for execution on theirassociated load and generation devices. When no supervisory controlleris connected, a group-wide decision is made using consensus techniquessuch as ratio-based average consensus or min-max consensus. In eithercase, individual NLCUs quickly execute set point commands they aregiven, and the NLCG provides a coordinated grid primary frequencyresponse within about 2 seconds (or less, if defined as a custom valuelocally). The desired NLCG response time (<=2 seconds) can be set inadvance and used to determine the size and capability of each NLCGformed.

In this way, the techniques of the present disclosure may provideprimary frequency response across a wider grid and may do so even whenindividual NLCUs do not have sufficient capacity to make a meaningfuldifference. By coordinating not only loads and energy resources in eachunit, but also groups of units, larger frequency events can be addressedusing behind-the-meter resources that would otherwise be unavailable forsupport. Furthermore, using the techniques described herein, suchresources can modify operation fast enough to provide primary responseto such frequency events, alleviating some of the responsibility ofinertia-based methods. As opposed to autonomous/uncoordinatedtechniques, the techniques described herein may enable a morecoordinated and optimal utilization of behind-the-meter resources forfrequency response.

FIG. 4 is a flow diagram illustrating example operations for performingcoordinated net-load management, in accordance with one or more aspectsof the present disclosure. FIG. 4 represents only one example processfor performing coordinated net-load management, and various otheradditional or different operations may be used in other examples.Furthermore, while described in the example of FIG. 4 as being performedby certain devices, some or all operations of FIG. 4 may be performed bydifferent devices than those described. The example operations of FIG. 4are described below within the context of FIG. 1.

In the example of FIG. 4, a PCC SCCN may determine, based on a frequencyvalue of an electrical network and a nominal frequency value, whether afrequency anomaly event has occurred (502). For instance, PCC SCCN 114(e.g., containing a measurement unit) may measure f(t_(e)) and evaluatef(t)<(f_(norm)−δ_(f,low)) and/or f(t)>(f_(nom)+δ_(f,high)) to determinewhether an underfrequency event or overfrequency event has occurred. Ifno frequency event has occurred, PCC SCCN 114 may continue to monitorthe grid frequency or perform one or more actions unrelated to thepresent disclosure. If a frequency anomaly event is detected, the PCCSCCN may output an indication that a frequency anomaly event hasoccurred (502). For instance, PCC SCCN 114 may output f(t_(e)) andP_(G,grid)(t_(e)).

In the example of FIG. 4, a management device may receive an indicationthat a frequency anomaly event has occurred (506). For instance,management device 103 may receive the grid frequency and grid powermeasurements. The management device may output a request for presentoperating power values (508). For instance, management device 103 mayoutput a request for the present operating power value of inverter 106and each of deferrable loads 108.

In the example of FIG. 4, inverter SCCN(s) and load SCCN(s) may receivethe request for present operating power values (510). Responsive toreceiving the request, the inverter SCCN(s) and load SCCN(s) may eachoutput an indication of the respective present operating value (512).For instance, inverter SCCN 116 may receive the request, measureP_(G,inv) for inverter 106, and output the latest operating power andoperating capacity limits (e.g., (−P_(G,inv) ^(max), P_(G,inv) ^(max))).Each of load SCCNs 118 may receive the request, measure the latest powerconsumption of the respective deferrable load, P_(Ld,i)(t_(e)), andoutput that value.

In the example of FIG. 4, the management device may receive the presentoperating power values (514). The management device may determine arespective power command for at least one of the energy resources and/orat least one of the deferrable loads (516). For instance, managementdevice 103 may receive the present operating power values of inverter106 and deferrable loads 108. Management device 103 may utilize thepresent operating power values, the grid frequency, the nominalfrequency, and the grid power to determine power commands for at leastone of inverter 106 and/or deferrable loads 108. As one example,management device 103 may solve optimization problem (2)-(5) todetermine P*_(Ld,i) for each of deferrable loads 108 and P*_(inv) forinverter 106. As further described herein, Management device 103 maydetermine power commands based additionally or alternatively on othercriteria, including information received from a management device ofanother net-load unit and/or information received from a supervisorymanagement device.

In the example of FIG. 4, the management device may cause at least oneof the energy resources and/or deferrable loads to modify operationbased on the respective power command (518). For instance, managementdevice 103 may output dispatch commands to inverter SCCN 116 and/or loadSCCNs 118. SCCNs 116 and 118 may receive the commands and modifyoperating of their respective devices accordingly. For example, inverterSCCN 116 may issue a new power set point to inverter 106 and load SCCNs118 may cease to provide power to, or modulate power supplied to,deferrable loads 108. The techniques of the present disclosure may beadditionally or alternatively described by one or more of the followingexamples.

EXAMPLE 1

A device comprising: at least one processor communicatively coupled toat least one energy resource controller that controls at least oneenergy resource and to at least one deferrable load controller thatcontrols power to at least one deferrable load, wherein the at least oneprocessor is configured to: receive an indication, determined based on afrequency value of an electrical network and a nominal frequency value,that a frequency anomaly event has occurred; and responsive to receivingthe indication that the frequency anomaly event has occurred: determine,for at least one of the at least one energy resource and the at leastone deferrable load, based on the frequency value, the nominal frequencyvalue, and a power value of the electrical network, a respective powercommand; and cause at least one of the at least one energy resource andthe at least one deferrable load to modify operation based on therespective power command.

EXAMPLE 2

The device of example 1, wherein determining the respective powercommand comprises: outputting a request for a respective presentoperating power value from each of the at least one energy resource andthe at least one deferrable load; receiving an indication of therespective present operating power value for each of the at least oneenergy resource and the at least one deferrable load; and determiningthe respective power command based additionally on the respectivepresent operating power value for each of the at least one energyresource and the at least one deferrable load.

EXAMPLE 3

The device of any of examples 1-2, wherein the respective power commandis determined based additionally on a specified control objective.

EXAMPLE 4

The device of example 3, wherein the specified control objectivecomprises at least one of: minimizing a total amount of deferrable loadthat must be curtailed; or prioritizing unmodified operation of specificones of the at least one deferrable load.

EXAMPLE 5

The device of any of examples 1-4, wherein the frequency anomaly eventcomprises an underfrequency event in which the frequency value issmaller than the nominal frequency value less a nominal frequency limitvalue; determining the respective power command comprises: determining,based on a present power value of the electrical network, the frequencyvalue and the nominal frequency value, a necessary power delta value;and determining whether the necessary power delta value is larger than adifference between a maximum rated power output value for the at leastone energy resource and a present power output value for the at leastone energy resource; and causing at least one of the at least one energyresource and the at least one deferrable load to modify operationcomprises causing, responsive to determining that the necessary powerdelta value is not larger than the difference, the at least one energyresource controller to increase a power output of the at least oneenergy resource by the necessary power delta value.

EXAMPLE 6

The device of example 5, wherein: the at least one deferrable loadcomprises a plurality of deferrable loads, each corresponding to arespective present load value in a plurality of present load values;determining the respective power command further comprises, responsiveto determining that the necessary power delta value is larger than thedifference, determining, based on the plurality of present load values,a set of deferrable loads in the plurality of deferrable loads that willbe curtailed; and causing at least one of the at least one energyresource and the at least one deferrable load to modify operationcomprises causing, responsive to determining the set of deferrableloads, a respective deferrable load controller for each deferrable loadin the set of deferrable loads to cease providing power to thedeferrable load.

EXAMPLE 7

The device of any of examples 1-6, wherein: the at least one processoris communicatively coupled to a second instance of the device; and therespective power command is determined based additionally on informationreceived from the second instance of the device regarding a net-loadunit managed by the second instance of the device.

EXAMPLE 8

The device of any of examples 1-7, wherein causing the at least one ofthe at least one energy resource and the at least one deferrable load tomodify operation based on the respective power command comprisesoutputting, to the at least one deferrable load controller, instructionsto cease providing power to the at least one deferrable load.

EXAMPLE 9

The device of any of examples 1-8, wherein causing the at least one ofthe at least one energy resource and the at least one deferrable load tomodify operation based on the respective power command comprisesoutputting, to the at least one energy resource controller, instructionsto modify an operating set point of the at least one energy resource.

EXAMPLE 10

The device of any of examples 1-9, wherein the at least one processor isconfigured to cause the at least one of the at least one energy resourceand the at least one deferrable load to modify operation within 200 msafter receiving the indication.

EXAMPLE 11

A system comprising: a grid point of common coupling (PCC) controllerconfigured to: measure a frequency value of an electrical distributionnetwork at a point at which the electrical distribution network connectsto a consumer electrical system; determine, based on the frequency valueand a nominal frequency value, whether a frequency anomaly event hasoccurred; and responsive to determining that the frequency anomaly eventhas occurred, output an indication of the frequency anomaly event; anet-load management device comprising at least one processor, whereinthe net-load management device is configured to: receive the indicationof the frequency anomaly event; output a request for a respectivepresent operating power value for at least one deferrable load in theconsumer electrical system; receive an indication of the respectivepresent operating value for the at least one deferrable load; responsiveto receiving the indication of the frequency anomaly event, determine,for the at least one deferrable load, based on the respective presentoperating value, the frequency value, and a nominal frequency value, arespective power command; and output an indication of the respectivepower command; and at least one deferrable load controller operativelycoupled to the at least one deferrable load, the at least one deferrableload controller configured to: receive the indication of the respectivepower command; and cause the at least one deferrable load to modifyoperation based on the respective power command.

EXAMPLE 12

The system of example 11, wherein: the net-load management device isfurther configured to: output a request for a respective presentoperating power value for at least one energy resource in the consumerelectrical system; and receive an indication of the respective presentoperating value for the at least one energy resource; determining, therespective power command comprises determining a respective powercommand for at least one of the at least one energy resource and the atleast one deferrable load; and the system further comprises at least oneenergy resource controller operatively coupled to the at least oneenergy resource, the at least one energy resource controller configuredto: receive the indication of the respective power command; and issue aset point to the at least one energy resource based on the respectivepower command.

EXAMPLE 13

The system of example 12, wherein: the frequency anomaly event comprisesan underfrequency event in which the frequency value is smaller than thenominal frequency value less a nominal frequency limit value;determining the respective power command comprises: determining, basedon a present power value of the power distribution network, thefrequency value and the nominal frequency value, a necessary power deltavalue; and determining whether the necessary power delta value is largerthan a difference between a maximum rated power output value for the atleast one energy resource and a present power output value for the atleast one energy resource; and outputting the indication of therespective power command comprises outputting, responsive to determiningthat the necessary power delta value is not larger than the difference,an instruction to cause the at least one energy resource controller toincrease a power output of the at least one energy resource by thenecessary power delta value.

EXAMPLE 14

The system of example 13, wherein: the at least one deferrable loadcomprises a plurality of deferrable loads, each corresponding to arespective present load value in a plurality of present load values;determining the respective power command further comprises, responsiveto determining that the necessary power delta value is larger than thedifference, determining, based on the plurality of present load values,a set of deferrable loads in the plurality of deferrable loads that willbe curtailed; and outputting the indication of the respective powercommand comprises outputting, responsive to determining the set ofdeferrable loads, instructions to a respective deferrable loadcontroller for each deferrable load in the set of deferrable loads tocease providing power to the deferrable load.

EXAMPLE 15

The system of any of examples 11-14, wherein: the grid PCC, the net-loadmanagement device, and the at least one deferrable load are part of afirst net-load unit; the net-load management device is a first net-loadmanagement device; the first net-load management device is furtherconfigured to receive second net-load information about at least one ofan energy resource included in a second net-load unit or a deferrableload included in the second net-load unit; and the first net-loadmanagement device is configured to determine the respective powercommand based additionally on the second net-load information.

EXAMPLE 16

The system of example 15, wherein the first net-load management deviceis further configured to output, to at least one of a supervisorymanagement device or a second net-load management device that managesthe second net-load unit, an indication of the respective presentoperating value for the at least one deferrable load.

EXAMPLE 17

The system of any of examples 11-16, wherein the net-load managementdevice is configured to determine the respective power command basedadditionally on a specified control objective that comprises at leastone of: minimizing a total amount of deferrable load that must becurtailed; or prioritizing unmodified operation of specific ones of theat least one deferrable load.

EXAMPLE 18

The system of any of examples 11-17, wherein the at least one deferrableload controller is configured to cause the at least one deferrable loadto modify operation by outputting, to the at least one deferrable load,instructions to modify an operating set point of the at least onedeferrable load.

EXAMPLE 19

The system of any of examples 11-18, wherein the at least one deferrableload controller is configured to cause the at least one deferrable loadto modify operation by ceasing to provide power to the deferrable load.

EXAMPLE 20

A method comprising: receiving, by a computing device comprising atleast one processor, an indication, determined based on a frequencyvalue of an electrical network and a nominal frequency value, that afrequency anomaly event has occurred, wherein the computing device iscommunicatively coupled to at least one energy resource controller thatcontrols at least one energy resource and to at least one deferrableload controller that controls power to at least one deferrable load; andresponsive to receiving the indication that the frequency anomaly eventhas occurred: determining, by the computing device and for at least oneof the at least one energy resource and the at least one deferrableload, based on the frequency value, the nominal frequency value, and apower value of the electrical network, a respective power command; andcausing, by the computing device, at least one of the at least oneenergy resource and the at least one deferrable load to modify operationbased on the respective power command.

The techniques of the present disclosure provide a framework forprovision of fast primary frequency response using coordinateddeferrable loads and energy resources such as DERs. This approach hasthe unique aspect of providing a fast response appropriate for primaryfrequency control but doing so using a group of net-load resources thatis coordinated in real-time in order to maximize local objectives. Thetechniques disclosed herein are flexible such that a variety ofdeferrable load and energy resource devices can be controlled usingconfigurable SCCNs and such that a variety of objectives for the optimalnet-load management scheme can be defined. The use of this approach inaggregation may enable wide-spread flexible load and DERs to providesignificant grid ancillary services that will help stabilize theemerging low-inertia grid.

In one or more examples, the techniques described herein may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over, as one or more instructions or code, acomputer-readable medium and executed by a hardware-based processingunit. Computer-readable media may include computer-readable storagemedia, which corresponds to a tangible medium such as data storagemedia, or communication media, which includes any medium thatfacilitates transfer of a computer program from one place to another,e.g., according to a communication protocol. In this manner,computer-readable media generally may correspond to (1) tangiblecomputer-readable storage media, which is non-transitory or (2) acommunication medium such as a signal or carrier wave. Data storagemedia may be any available media that can be accessed by one or morecomputers or one or more processors to retrieve instructions, codeand/or data structures for implementation of the techniques described inthis disclosure. A computer program product may include acomputer-readable storage medium.

By way of example, and not limitation, such computer-readable storagemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage, or other magnetic storage devices, flashmemory, or any other medium that can be used to store desired programcode in the form of instructions or data structures and that can beaccessed by a computer. Also, any connection is properly termed acomputer-readable medium. For example, if instructions are transmittedfrom a website, server, or other remote source using a coaxial cable,fiber optic cable, twisted pair, digital subscriber line (DSL), orwireless technologies such as infrared, radio, and microwave, then thecoaxial cable, fiber optic cable, twisted pair, DSL, or wirelesstechnologies such as infrared, radio, and microwave are included in thedefinition of medium. It should be understood, however, thatcomputer-readable storage media and data storage media do not includeconnections, carrier waves, signals, or other transient media, but areinstead directed to non-transient, tangible storage media. Disk anddisc, as used herein, includes compact disc (CD), laser disc, opticaldisc, digital versatile disc (DVD), floppy disk and Blu-ray disc, wheredisks usually reproduce data magnetically, while discs reproduce dataoptically with lasers. Combinations of the above should also be includedwithin the scope of computer-readable media.

Instructions may be executed by one or more processors, such as one ormore digital signal processors (DSPs), general purpose microprocessors,application specific integrated circuits (ASICs), field programmablelogic arrays (FPGAs), or other equivalent integrated or discrete logiccircuitry. Accordingly, the term “processor,” as used herein may referto any of the foregoing structure or any other structure suitable forimplementation of the techniques described herein. In addition, in someaspects, the functionality described herein may be provided withindedicated hardware and/or software modules. Also, the techniques couldbe fully implemented in one or more circuits or logic elements.

The techniques of this disclosure may be implemented in a wide varietyof devices or apparatuses, including a wireless handset, an integratedcircuit (IC) or a set of ICs (e.g., a chip set). Various components,modules, or units are described in this disclosure to emphasizefunctional aspects of devices configured to perform the disclosedtechniques, but do not necessarily require realization by differenthardware units. Rather, as described above, various units may becombined in a hardware unit or provided by a collection ofinter-operative hardware units, including one or more processors asdescribed above, in conjunction with suitable software and/or firmware.

The foregoing disclosure includes various examples set forth merely asillustration. The disclosed examples are not intended to be limiting.Modifications incorporating the spirit and substance of the describedexamples may occur to persons skilled in the art. These and otherexamples are within the scope of this disclosure and the followingclaims.

What is claimed is:
 1. A device comprising: at least one processorcommunicatively coupled to an energy resource controller that controlsan energy resource and to a deferrable load controller that controlspower to a deferrable load, wherein the at least one processor isconfigured to: receive an indication, determined based on a frequencyvalue of an electrical network and a nominal frequency value, that afrequency anomaly event has occurred; and responsive to receiving theindication that the frequency anomaly event has occurred: determine, forat least one of the energy resource or the deferrable load, based on thefrequency value, the nominal frequency value, and a power value of theelectrical network, a power command; and cause at least one of theenergy resource or the deferrable load to modify operation based on thepower command.
 2. The device of claim 1, wherein determining the powercommand comprises: outputting a request for a respective presentoperating power value from each of the energy resource and thedeferrable load; receiving an indication of the respective presentoperating power value for at least one of the energy resource or thedeferrable load; and determining the power command for the at least oneof the energy resource or the deferrable load based additionally on thereceived indication of the respective present operating power value. 3.The device of claim 1, wherein the power command is determined basedadditionally on a specified control objective.
 4. The device of claim 3,wherein the specified control objective comprises at least one of:minimizing a total amount of deferrable load that must be curtailed; orprioritizing unmodified operation of specific ones of the at least onedeferrable load.
 5. The device of claim 1, wherein: the frequencyanomaly event comprises an underfrequency event in which the frequencyvalue is smaller than the nominal frequency value less a nominalfrequency limit value; determining the power command comprises:determining, based on a present power value of the electrical network,the frequency value and the nominal frequency value, a power deltavalue; and determining whether the power delta value is larger than adifference between a maximum rated power output value for the energyresource and a present power output value for the energy resource; andcausing at least one of the energy resource or the deferrable load tomodify operation comprises causing, responsive to determining that thepower delta value is not larger than the difference, the energy resourcecontroller to increase a power output of the energy resource by thepower delta value.
 6. The device of claim 5, wherein: the deferrableload comprises one in a plurality of deferrable loads, eachcorresponding to a respective present load value in a plurality ofpresent load values; determining the power command further comprises,responsive to determining that the power delta value is larger than thedifference, determining, based on the plurality of present load values,a set of deferrable loads in the plurality of deferrable loads that willbe curtailed; and causing at least one of the energy resource or thedeferrable load to modify operation comprises causing, responsive todetermining the set of deferrable loads, a respective deferrable loadcontroller for at least one deferrable load in the set of deferrableloads to cease providing power to the deferrable load.
 7. The device ofclaim 1, wherein: the at least one processor is communicatively coupledto a second instance of the device; and the power command is determinedbased additionally on information received from the second instance ofthe device regarding a net-load unit managed by the second instance ofthe device.
 8. The device of claim 1, wherein causing the at least oneof the energy resource or the deferrable load to modify operation basedon the power command comprises outputting, to the deferrable loadcontroller, instructions to cease providing power to the deferrableload.
 9. The device of claim 1, wherein causing the at least one of theenergy resource or the deferrable load to modify operation based on thepower command comprises outputting, to the energy resource controller,instructions to modify an operating set point of the energy resource.10. The device of claim 1, wherein the at least one processor isconfigured to cause the at least one of the energy resource and thedeferrable load to modify operation within 200 ms after receiving theindication.
 11. A system comprising: a grid point of common coupling(PCC) controller configured to: measure a frequency value of anelectrical distribution network at a point at which the electricaldistribution network connects to a consumer electrical system;determine, based on the frequency value and a nominal frequency value,whether a frequency anomaly event has occurred; and responsive todetermining that the frequency anomaly event has occurred, output anindication of the frequency anomaly event; a net-load management devicecomprising at least one processor, wherein the net-load managementdevice is configured to: receive the indication of the frequency anomalyevent; output a request for a respective present operating power valuefor a deferrable load in the consumer electrical system; receive anindication of the respective present operating power value for thedeferrable load; determine, based on the respective present operatingvalue for the deferrable load, the frequency value, and a nominalfrequency value, a power command; and output an indication of the powercommand; and a deferrable load controller operatively coupled to thedeferrable load, the deferrable load controller configured to: receivepower commands; and cause the deferrable load to modify operation basedon the received power commands.
 12. The system of claim 11, wherein: thenet-load management device is further configured to: output a requestfor a respective present operating power value for an energy resource inthe consumer electrical system; receive an indication of the respectivepresent operating power value for the energy resource; and determine thepower command based further on the respective present operating powervalue for the energy resource; and the system further comprises anenergy resource controller operatively coupled to the energy resource,the energy resource controller configured to: receive power commands;and issue a set point to the energy resource based on the received powercommands.
 13. The system of claim 12, wherein: the energy resourcecomprises one in a plurality of energy resources, each corresponding toa respective energy resource controller in a plurality of energyresource controllers; the frequency anomaly event comprises anunderfrequency event in which the frequency value is smaller than thenominal frequency value less a nominal frequency limit value;determining the power command comprises: determining, based on a presentpower value of the power distribution network, the frequency value andthe nominal frequency value, a power delta value; determining whetherthe power delta value is larger than a difference between a maximumrated power output value for at least a portion of the plurality ofenergy resources and a present power output value for the at least aportion of the plurality of energy resources; and responsive todetermining that the power delta value is not larger than thedifference, generating a command to cause an energy resource controllerin the plurality of energy resource controllers to increase a poweroutput of a corresponding energy resource.
 14. The system of claim 13,wherein: the deferrable load comprises one in a plurality of deferrableloads, each corresponding to a respective deferrable load controller ina plurality of deferrable load controllers and each corresponding to arespective present load value in a plurality of present load values; anddetermining the power command further comprises: responsive todetermining that the power delta value is larger than the difference,determining, based on the plurality of present load values, a set ofdeferrable loads in the plurality of deferrable loads that will becurtailed, and generating a command to cause a deferrable loadcontroller corresponding to a deferrable load in the set of deferrableloads to cease providing power to the deferrable load.
 15. The system ofclaim 11, wherein: the grid PCC, the net-load management device, and theat least one deferrable load are part of a first net-load unit; thenet-load management device is a first net-load management device; thefirst net-load management device is further configured to receive secondnet-load information about at least one of an energy resource includedin a second net-load unit or a deferrable load included in the secondnet-load unit; and the first net-load management device is configured todetermine the respective power command based additionally on the secondnet-load information.
 16. The system of claim 15, wherein the firstnet-load management device is further configured to output, to at leastone of a supervisory management device or a second net-load managementdevice that manages the second net-load unit, an indication of therespective present operating value for the at least one deferrable load.17. The system of claim 11, wherein the net-load management device isconfigured to determine the power command based additionally on aspecified control objective that comprises at least one of: minimizing atotal amount of deferrable load that must be curtailed; or prioritizingunmodified operation of specific ones of the at least one deferrableload.
 18. The system of claim 11, wherein the deferrable load controlleris configured to cause the deferrable load to modify operation byoutputting, to the deferrable load, instructions to modify an operatingset point of the deferrable load.
 19. The system of claim 11, whereinthe deferrable load controller is configured to cause the deferrableload to modify operation by ceasing to provide power to the deferrableload.
 20. A method comprising: receiving, by a computing devicecomprising at least one processor, an indication, determined based on afrequency value of an electrical network and a nominal frequency value,that a frequency anomaly event has occurred, wherein the computingdevice is communicatively coupled to an energy resource controller thatcontrols an energy resource and to a deferrable load controller thatcontrols power to a deferrable load; and responsive to receiving theindication that the frequency anomaly event has occurred: determining,by the computing device and for at least one of the energy resource orthe deferrable load, based on the frequency value, the nominal frequencyvalue, and a power value of the electrical network, a power command; andcausing, by the computing device, at least one of the energy resource orthe deferrable load to modify operation based on the power command.